1. Field of the Invention
This invention relates to a machine tool and more particularly to a machine tool equipped with an automatic tool changer (ATC).
2. Description of the Prior Art
In a machine tool such as a multi-purpose machining center (MC) for threading and cutting holes in work pieces, a number of taps and drills are stored in a predetermined place before machining. Using an ATC, the tool being used can be exchanged with another type tool or a new one, automatically. Various kinds of ATC's have been proposed, and one ATC having a relatively simple construction has been disclosed in Japanese Pat. Appln. Laid-Open No. 58-51046. In that ATC, a disk tool magazine with many tools radially arranged is rotatably mounted on a main spindle and reciprocates with the main spindle during non-tool changing machining operations. The tool magazine can slide relative to the main spindle head only when the main spindle head reaches the automatic tool changing region which is located directly above its machining region, that is, the region wherein the main spindle head normally moves up and down for machining purposes. In a machine tool with this type of ATC, the main spindle head first is slid upwardly relative to the tool magazine to extract the used tool from the toe of the main spindle. Subsequently, the tool magazine is rotatingly indexed to allow a replacement tool to move beneath the main spindle with their respective axis aligned. The main spindle then slides downward to capture the new tool.
Serious disadvantages can exist in a machine tool having an ATC of such a construction. Because the tool magazine moves together with the main spindle head during machining operations, tools mounted on the tool magazine and extending in the radial direction can interfere with the work piece being machined, depending on the shape of the work piece. Another disadvantage is that a machine tool with such an ATC can be quite complicated in construction, be prone to develop trouble, and be relatively expensive.